A former elk farm owner was found not guilty Friday of releasing wild pigs into the western Wisconsin countryside after a judge said the witnesses against him weren't credible.

Robert S. Johnson, 55, of San Marcos, Texas, faced one count of illegally stocking wild animals, a civil offense. State investigators had accused him of bringing about 31 wild hogs from Texas to Crawford County in 2002, spawning a feral hog population that has caused thousands of dollars in crop damage.

The state Department of Justice was seeking $31,000 in forfeitures from Johnson — $1,000 for each pig — as well as an unspecified amount of money to cover environmental damage.

But Crawford County Judge Michael Kirchman said the evidence against Johnson was circumstantial. The state's key witness, a man who claimed to have watched Johnson release the pigs near the Kickapoo River, wasn't believable, Kirchman said.

Johnson faces trial in November on federal charges of illegally moving elk from his Wisconsin farm to Illinois, but said he was happy Kirchman found in his favor in the pig case.

"This has been hanging over my head," Johnson said as he left the courtroom. "Now just one more thing to clear up."

Kirchman's decision means the state still hasn't held anyone responsible for bringing the wild pigs to Crawford County. Assistant Attorney General Cynthia Hirsch, who prosecuted Johnson, acknowledged the case was an uphill fight and said she would speak to the state Department of Natural Resources before deciding whether to appeal.

Biologists estimate feral hogs roam at least 25 states. They can weigh up to 450 pounds and love to root in the earth for food, wrecking crops and the landscape. The U.S. Department of Agriculture estimates they cause about $800 million in damage to the nation's farm industry each year.

Wild pigs aren't native to Wisconsin, but they started appearing in the state around 2000, according to the DNR. No one has firm figures on how large the population is statewide or how much total damage the animals have caused. Some farmers say the pigs have cost them tens of thousands of dollars in lost crops.

Crawford County has been a hog hot spot. Hirsch told Kirchman the DNR believes the pigs first appeared in the county in 2002. About 275 pigs have been killed in the county since then.

The state's case against Johnson hinged on Kirby Fulbright of Medina, Texas. Fulbright told wardens from Wisconsin, Texas and Illinois and a USDA agent in March 2007 he helped trapped pigs on his property for Johnson. He said he and Johnson drove to Wisconsin in the spring of 2002 with a trailer loaded with 31 hogs and he watched Johnson release them into the wild near his ranch outside Gays Mills.

But Fulbright recanted his statement a week or so later, saying he was drunk during the interview and told the wardens what they wanted to hear.

Johnson's attorney, Mark Peterson, painted Fulbright as unreliable. He pointed to a USDA agent's report that said Fulbright was drunk when he was interviewed.

Mike Cross, a Wisconsin warden, and Mike Lyne, an Illinois warden, were among the investigators who interviewed Fulbright. They both testified Friday that Fulbright was sober. Lyne said Fulbright drank two vodka and orange juices near the end of the interviews but wasn't drunk.

Johnson, a tall man with reddish-blond hair and a mustache, testified in his own defense. He said he traveled from Texas to Wisconsin in February or March of 2002 with an empty trailer. He said he planned to buy hay in Wisconsin, where bales cheaper than in Texas. He denied he released any pigs and said it would have made no sense.

"There's no benefit at all for me," he said.